Centrifugal fluid jet pulverizer



A. C. HOBBIE CENTRIFUGAL FLUID JET PULVERIZER rgb. 2o 1940.

2 Sheets-Sheet J.

Filed Sept farli/riff 55 BY ma e A@ '/A ORNEYS.

Patented Feb. 20, Y

CETRIFUGAL FLUID JET PULVEBIZER Albert C. Bobbie, Moorestown, N. J., asnignor to International Pnlverizing Corporation, Camden, N. J., a corporation of New Jersey Application september 1,1937, serial-Ne.' 161,934

3 Claims.

'I'his invention relates to apparatus for pulverizing or size reduction of solid materials by centrifugal fluid jet action, and particularly topulverizing apparatus wherein jets of gaseous fluid are introduced at high velocity into an annular grinding zone in an outer portion of a treatment chamber of circular cross section, said grinding zone containing material to be pulverized in the form of discrete small pieces. 'I'he high velocity fluid jets. or at least most of them, are intro-A duced in directions inclined forwardly in one direction with respect to radii of the treatment chamber, so as to maintain the fluid in the chamber in rapid whirling motion in the direction of such forward inclination, either clockwise or counterclockwise. The grinding zone is of limited axial length and is conilned by peripheral portions of the chamber walls enclosing said zone at its outer circumference and at both axial ends, and gaseous fluid is continually withdrawn inwardly from the grinding zone and discharged from the treatment chamber, preferably through a centrally disposed iluid outlet. The gaseous fluid thus has a general inwardly spiralling movement within the treatmentchamber, and the ma` terial to be pulverized is preferably continually introduced into the moving fluid within the treatment chamber.

The high velocity fluid jets effect a reduction of particle size of the material under treatment by impact and attrition of particles against one another and against the chamber walls, While at the same timecausing the charge of material to rotate rapidly within the grinding zone in the direction of the whirling movement of the fluid. Due to the centrifugal eiTects resulting from the rapid rotationof the charge within the grinding zone, the larger particles are caused to circulate in said zone Where they come repeatedly under the influence of the introduced high velocity jets and are thus repeatedly subjected to the size reducing action produced thereby, while the material which is suilciently reduced in size is entrained by the gaseous fluid as it spirals inwardly toward the centrally disposed iiuid outlet.

The entraining action of the inwardly spiralling gaseous uid exerts on the suspended particles of the circulating material within the pulverizing zone a radially inward component opposing the radially outward component due to centrifugal action, and continuously removes from the grinding zone particles which are sufliciently reduced in size. entraining su'ch particles toward the fluid outlet and effecting a very intense, fluid-sweeping action oi' the charge within the chamber, to-

gether with a high degree of -centrifugal classification of the entrained material. A portion 'of the chamber radially inwardly from the grinding zone may communicate with an axially extended centrifugal product collector of smaller diameter than the chamber, which utilizes the whirling energy of the gaseous fluid entering said collector to separate a considerable portion of the entrained material from the carrier liuid, while the fluid, more or less freed of such material, may be discharged through the axially or centrally disposed fiuid outlet which is of smaller diameter than the collector and may, if desired, be subjected to a further' separating action outside the Vchamber to remove a further quantity of solid material therefrom. The outer circumference of the centrifugal product collector is preferably spaced av considerable distance radially inward from the annular grinding zone into which the high velocity iiuid jets are introduced, so that the above described centrifugal classifying action isv maintained not only within the grinding zone but also in an intermediate classifying zone, whereby particles which have not been sufliciently reducedin size are effectively prevented from inward entrainment to the product collector or to 4the central fluidA outlet and are caused to recirculate in the grinding zone until sulciently reduced. In some cases, the above described centrifugal product collector may be omitted, and all of the material which is suiilclently reduced may be discharged with the entraining gaseous `fluid through the centrally disposed outlet and may be separated and collected in any suitable manner outside the treatment chamber.

It is generally convenient and preferable to introduce the material to be pulverized into the treatment chamber at one or more positions inwardly of the zone of action of the highvelocity o jets, and preferably adjacent but within the inner boundary of the grinding zone, so that any material which is already sufliciently reduced to be entrained and carried inwardly by the spiralling fluid is not causedto be subjected to further grinding action, while particles of larger size are caused by centrifugal action to move outwardly into the grinding zone. Furthermore, it is generally convenient to introduce this material into the treatment chamber in suspension in a gaseous uid having a component of motion in the direction of whirling fluid movement induced by the high velocity fluid jets.

The present invention is concerned with the grinding zone of such fluid jet pulverizing apparatus, and particularly with the Amanner in which the high velocity nuidjets are introduced into said zone and the conguratlon of the peripheral walls of said zone, and it will be understood that the features of' this invention may be employed in any centrifugal fluid jet pulverizing apparatus of provide for highly effective utilization of the energy of the high velocity fluid jets in effecting size reduction of the material by impact and.

attrition; to provide improved means for bringing the material under the influence of the high velocity uid jets; and to minimize or reduce the wear on the walls of the grinding zone.

In centrifugal fluid jet pulverizers the diameter of the openings through which the high velocity fluid jets are introduced into the grinding zone is small compared to the axial length of said zone. As the circulating material is more or less free to distribute itself throughout the axial length of the grinding zone, it will be evident that only a small portion of this material will be directly intercepted by a high velocity jet in moving past the angular position of the jet. Consequently, only a relatively small or limited portion of tlie circulating material is intercepted by the fluid jets during each complete rotation of the material about the axis of the treatment chamber. It is possible for some material to circulate for considerable lengths of time inplanes axially removed from the plane or planes of the jets, and it is necessary to depend upon random mixing induced by frictional eddes at the periphery of the chamber in order to ultimately bring all the material within the zone of action of the jets. i

An important object of the invention, there fore, is to provide jet openings so directed into l the annular'grinding zone that the high velocity uid jets issuing from said openings will cause a positive circulatory motion within said grinding zone in radial planes through the axis; of the treatment chamber, to be superimposed upon the generaloirculation of the charge around the axis of the chamber, in order to direct the circulating material positively into the ,zones of action of the issuing jets.

A further object of the invention is to provide, in a pulverizing apparatus having jet openings so directed as to superimpose they above described circulatory motion in radial lplanes upon the rotationof the material about the axis of the chamber, a treatment chamber in which the peripheral wall portions extending around and at both axial ends of the grinding zone are of curved configuration `in radial planes through the axis conforming generally tothe curvature of the superimposed circulatory motion produced by the fluid jets, so as to assist in maintaining such circulatory motion of the material and in the resulting positive movement of the material into the zones of action of the jets.

In centrifugal fluid jet pulverizers having one or more pairs of opposed jet openings so directed as` to maintain the rotation of. the material in the chamber and having-opposed axial components directed toward each other to cause impacts of particles projected by the jets, it is found that when these jets are located suillcient'ly close t the periphery 0i the chamber to intercept and act upon the circulating material, there is a localized region of intense wear at the peripheral walls adjacent the intersection of two such opposed jets due to the vigorous sand blasting action resulting from the random scattering of impacting particles.

A further object of the present invention, in a preferred embodiment, is to provide a centrifugal fluid jet pulverizer having one or more pairs of opposed jet openings, directed as above described but located radially inwardly from the periphery of the treatment chamber a sumcient distance to greatly reduce or minimize the localized wear on the peripheral Walls resulting from sand blasting action due to scattering of the impacted particles. In order to effectively reduce or avoid this localized wear when using opposed jets, it is necessary that not only the jet openings themselves, but also the positions of intersection of the opposed jets, be inwardly removed from the periphery of the chamber. In centrifugal fluid jet pulverizers of the prior art, jets so located would be relatively ineffective because the material to be pulverized would circulate largely adjacent the periphery of the chambers and outside the zone of action of the jets.

Accordingly, it is a further object of my inventon to provide, in conjunction with opposed fluid jets located inwardly from the periphery of the chamber as above described, other jet openings adjacent the'periphery of the chamber and so disposed and directed as to superimpose upon the general rotative motion of the circulating material about the axis of thechamber a component lof motion in a radial plane through the y axis of the chamber to direct the material positively into the zone of action of the opposed jets, thus eectively utilizing the increased shattering and pulverizing eiect of the opposed jets while eliminating or minimizing the localized wear which would result if portions of the chamber walls were closely adjacent the intersection of the opposed jets.

The accompanying drawings illustrate forms of centrifugal fluid jet pulverizing apparatus in accordance with my invention, and referring thereto:

Fig. 1 is a vertical section through the axis of a preferred form of such apparatus, with certain parts broken away;

Fig. 2 is a partly sectional plan view on line 2-2 in Fig. 1, with the topof the material supply passage partly broken away;

Fig. 3 is an enlarged vertical section on line Fig. 4 is a partial vertical section of a modled form of apparatus; and

Fig. 5 is a partial plan view of the form of apparatus shown in Fig. 4, showing an alternative arrangement of the jet openings.

The apparatus shown in Figs. 1 to 3 comprises `a casing of circular cross section enclosing a treatment chamber and including a top section I,

a bottom section l', and an intermediate ring stantially along arcs of circles in radial planes through the axis of the chamber. as shown in Fig. 1, from the juncture thereof with the flat top and bottom portions 5 and 5' to their outer edges where they join the ring section 2. The top and bottom sections are provided with annular uid pressure manifolds 1 and I disposed exteriorly of the curved rwall portions 6 and 6 respectively and having iiuid inlets 8 and 8'. The intermediate ring section 2 forms a peripheral wall whose upper and lower portions 9 and 9 are curved, in radial planes `through the axis of the chamber, preferably substantially along arcs of circles tangent to the curved wall portions B and 6' respectively and meeting one another at II. an annular-'pressure manifold I2 disposed ex teriorly of the walls 9 and 91 and having a fluid inlet I3.

It will be understood that the above described sectional construction of the casingis not essential to the invention, and is shown merely for the purpose of simplifying fabrication and assembly and at the same time facilitating access to the interior of the casing for cleaning, inspection or other purpose.

The outer portion of the treatment chamber within the casing may be defined as an annular grinding zone, and it will be seen that the curved peripheral wall portions E, 9, 9 and 6 extend around and at both axial ends of this grinding zone. These curved wall portions are provided with fluid jet openings communicating with the pressure manifolds and adapted to introduce high velocity fluid jets into the grinding zone, and said jet openings are so positioned and directed that the iiuid jets issuing therefrom will maintain the general rotation or whirling motion `of the material to be pulverized about the axis of the chamber and will also superimpose thereona.

positively circulatory motion having components in radial planes passing through the axis of the chamber. As may beseen from Figs. 1 and 2, I have shown four sets of jet openings, at 90 intervals around the circumference of the chamber, the position of the respective sets of jet openings being indicated at A, B, C and D in Fig. 2. It will be understood, however, that any desired number and angular spacing of these jet openings around the circumference of the chamber may be employed.

The annular grinding zone may be considered as comprising two portions Z and Z' lying respectively above and below a median horizontal plane through the circular line at II defined by the juncture of the upper curved wall portion 9 and the lower curved wall portion 9 of the intermediate casing section 2. The upper portion of this grinding zone is defined by the curved wall portions 6 and 9 whose center of curvature, in any plane passing through the axis of the chamber (such as the plane of Fig. 1) is indicated at O, while the lower portion of this zone is defined by the curved wall portions 6 and 9' whose center of curvature in such a plane is indicated at O and is axially spaced from the point O. Each set of jet openings is shown as comprising a plurality of openings such as Ila, I5a, and IIia at different angular positions about the center O, for delivering gaseous fluid at high velocity into the upper portion of the grinding zone, the direction of the axis of each opening having a component inclined inwardly toward the interior of the treatment chamber and forwardly in one direction (clockwise in Fig. 2) with respect to the radius of the treatment chamber at the position of that opening, as indicated in Fig. 2 by the This section is also provided with 1 bythe dotted projection traces of said axes upon a radial vertical plane passingthrough the axis of the treatment chamber. Each set of jet openings further comprises a plurality of openings' Ila', I5a'- and IBa' at different angular positions about thecenter of curvature O', for delivering gaseous uid at high velocity into the lower portion of the grinding zone, the axis forward inclinationrwith respect to radii of the treatmentchamber in the same manner as above described and also having a component inclined inwardly toward the interior of the treatment chamberand ina direction opposite to that of the jet openings in the upper portion l(counterclockwise at the'rleft side of Fig. 1) with respect to a radial line from the position of that opening to the center. of curvature O', as also indicated in Fig. 1 by the dotted projection traces of the jet axes upon a radial vertical plane passing through the axis of the treatment chamber. The jet openings 15a and IBa are shown as extending through the curved wall portion 6 of the upper casingxsection I with the pressure manifold 1; the jet openings Ida and Ila as extending through the curved wall portions 9 and 9' respectively of the intermediate casing section 2 and communicating with -the pressure manifold I2; and the jet openings I5a and I6a as extending through the curved wall portion 6' of the lower casing section I and communicating with the pressure manifold 1', but it will be understood that any desired arrangement of pressure manifolds or conduits may be employed` for. placing these jet openings in communication with,a source of fluid under pres- Sure. i

The component of inclination of the jet openings forwardly with respect to radii of the treatment chamber causes the high velocity iiuid jets introduced therethrough to maintain a general whirling movementof gaseous fluid and material to be reduced about the axis of the treatment chamber, in a clockwise direction, as indicated by the arrow in Fig. `2, while the components of inclination of the several openings with-respect to radii through the centers of curvature O and O' of the walls of the grinding zone cause such iiuid jets to superimpose upon this general whirling movement a circulatory motion in radial vertical planes through the axis of the treatment chamber. This latter motion is clockwise in the upper portion,` and counterclockwise in the lower portion of the grinding'zone at the left side of Fig. 1, as indicated by the arrows in that ligure.

It will be observed that the jet openings I6a and I 6a' are substantially opposite one another in a direction parallel to the axis of the treat- Yment' chamber, and haveopposed components directed toward each other and parallel to said axis, that is, the opening I 6a has a component directed vertically downward and the opening IGa' has a componentl directed vertically upward. Since these openingsalso have components directed forwardly in the direction 'of general whirling movement about the axis of the treating chamber, the fluid jets introduced therethrough will be inclined toward each other as indicated and communicating Aof each of these openings having a component of in Fig. 3 by the dotted projection traces of the jet axes upon the plane of said figure, and will intersect one another at a position somewhat beyond the position of said openings in the' direction of said whirling movement, as at X.

It will be understood that as the iluid jets enter the treatment chamber they will gradually expand in diameter. The jet openings shown at llc', lic' and iBc' represent openings of the set C corresponding -to the ,openings Ila', IIa' and Ita' of set A. The iiuid jet issuing from opening I6c' will expand as indicated, for example, at J, and the position of intersection thereof with the opposing jet (from opening itc in llig.l 1) may be as indicated, for example, at X' in Fig. 2. The opposed openings, such as lia, lia', and lic, lic', are located radially inwardly from the periphery of the treatment chamber, and it will be seen that` the positions and directions of these openings are such that the oppositely directed jets issuing therefrom will intersect one another at positions (such as X') which are also inwardly removed from the periphery of the chamber, thereby avoiding excessive wear on the walls of the chamber due to the sand blasting action of impacting particles acted upon by such jiets, as discussed above. The remaining jet openings of each set, such as openings ila, IM, ila' and ISa' of set A and openings Hc, lic, llc' and I5c of set C, are located closer to the periphery of the treatment chamber and at greater radial distances from the axis of the chamber than the openings Isa, |6a, iGc and I6c of the correspending sets, so that the fluid jets issuing from said other jet openings are adapted to act upOn the materal which tends to accumulate by centrifugal action in the peripheral portions of the grinding zone, i. e., in the portions of said zone which are at the greatest radial distance from the axis of the chamber. Thus, as will be described more fully hereinafter, by locating the jets of each set at a plurality of different distances from the axis of the casing, the material which is carried by centrifugal force outwardly toward the periphery of the casing is picked up and positively directed into positions where it can be acted upon by jets inwardly removed from the periphery.

'I'he other parts of the apparatus may be substantially as described in U. S. Patent No. 2,032,827 and are shown as comprising a centrifugal product collector 2l associated with and extending through the bottom wall 5', a centrally disposed uid outlet passage 22 associated with and extending through the top wall 5, andsuitable means for feeding divided solid material into the treatment chamber. The centrifugal product collector 2| is of materially less diameter than the inner diameter of the grinding zone and opens at its upper end 23 into the treatment chamber. Any suitable storing means may be provided at the lower end of the centrifugal product collector to provide for either intermittent or continuous discharge of collected material therefrom, preferably in such manner as tovsubstantially avoid iniiow or outflow of air or gas. 'Ihe outlet pipe 22 is of smaller diameten than the product collector 2| and is shown as opening at its lower end 24 into the interior of the treatment chamber at a position somewhat above the upper .end of the product collector. i

The means forintroducing divided solid material is shown as comprising anlannular supply passage or manifold 25 associated with the top wall 5 and lcommunication with the interior of the treatment chamber through a plurality of 'openings 26 in said top wall, said openings being inclined downwardly and forwardly in the direction'of the above described whirling movement of the gaseous fluid within the chamber around the axis thereof, a passage 21 through which a suitable gaseous fluid is supplied to the annular chamber 2l in a downwardly and forwardly inclined direction conforming to the direction of said whirling movement and provided with means such as a nozzle 22 for creating a reduced pressure therein, and a hopper 29 for feeding divided solid material into the passage 21 at the position of such reduced pressure.

In operation of the apparatus, a gaseous uid at high pressure is continuously supplied to the manifolds 1,1' and I2 through the inlets 8, I' and I2. Such fluid may be either air or other permanent gas from a compressor or other suitable source of high pressure, or may be dry steam from a high pressure boiler, and may be introduced. for example, at a pressure between about 50 and 500 pounds per square inch or more. This gaseous iluid is delivered from the manifolds through .iet openings ila, lia, Ia, etc., in the form of vhigh velocity jets directed as above described.

'I'he jet openings are of suillciently small size with relation to the dimensions of the apparatus, so that fluid iets of the desired high velocity may be introduced therethrough without causing an excessive total flow of gaseous iluid through the treatment chamber which might prevent classiflcation at the desired particle size. While the jet openings are shown as. being simply openings through the walls of the treatment chamber, it will be understood that suitable replaceable nozzles having small orifices may be provided if desired.

As explained above, the fluid jets serve not only to maintain the whirling movement of the contents of the treatment chamber around the axis thereof but also to superimpose upon this general whirling motion a circulatory motion inv radial vertical planespassing through the axis oi the chamber. Due to the inward movement of the iluid toward the outlet pipe 22, the resulting composite motion of the uid is further modified to produce an inward spiralling thereof.

Thedivided solid material to be treated is introduced through the annular supply passage 25 as above described and is delivered, in suspension in the gas supplied through passage 21, through the inclined material supply openings 26, so that as the material enters the treatment chamber it has an initial motion conforming to the direction of whirling movement of the gaseous fluid in said chamber. The particles of material are picked up and carried forwardly around the axis of the treatment chamber, in the direction of this whirling movement (clockwisein Fig. 2). Due to cen- -trifugalactiom particles above a certain size are caused to move outwardly into the annular grinding zone and into the zones of action of the high velocity uid jets delivered throughthe openings Ila, lia, Ita, etc.

The following description of the action of the uid jets will refer particularly to the .iets introduced through' the openings at the position A in Fig. 2, but it will be understood that the same description will also be applicable to the other sets of jets, such as those at .B, C and D.

The jets introduced through the openings ila vand lia in Fig. 1 inthe upper portion Z of the grinding zone will impart a spirallingmotion, similar to that of a right handed screw, to the material accumulating along the torus-like surface denned by the curved wall portions 9 and l, so as to direct such material into thepath of the jetV introduced through opening Ita. .Similarly, the jets introduced through openings ila' and Na' willimpart a spiralling motion, similar to that of a left-handed screw, to the material accumulating along the torus-like surface, deilned by the curved wall portions 9 and 6 in the lower portion Z' of the grinding zone, so as to direct such material into the path of the jet introduced through opening lia.

While the several jet openings Ha, |a, etc., are shown as located in the same radial plane passing through the axis of the treatment cham` ber, this construction is shown'primarily for the purpose of simplifying the illustration in Fig. 1, and would ordinarily be used only when the several sets of jet openings such as A. B. C, etc.. are disposed at suillciently small angular intervals around the treatment chamber, so that the jets through the respective openings such as Ila and I5a, will serve to direct material into the path of a jet of the next set. When the design `of the apparatus does not contemplate the provision of a suiliciently large number of sets of jets to produce the above described result, a preferred arrangement wouldsbe to stagger the jet openings of each set so that the positions of the successive jet openings such as I 4a, I5a and Ita of each set, will conform substantially to the pathV of the above described spiralling motion of the material along the torus-like surfaces of the upper "and lower portions of the grinding zone. For example, the jet opening |5a of each set would be angularly displaced from the jet opening Ma in theV direction of whirling movement about the axis of the treatment chamber, and the jet opening I6a would be similarly displaced from the jet lopening lia. Such a staggered arrangement of the jet openings is described more fully hereinafter in connection with Fig. 5.

' Thus it will be seen that the fluid jets delivered through the openings, such as Ila and |5a," Ila and lia', will act upon material tending to accumulate through centrifugal action in the portions of the grinding zone which are at the greatest radial distance from the axis of the treatment chamber, and will positively direct some of this materialinto the zones of action of the opposed Jets, `such as lia and Isa'.

It will be seen that the jets issuing through the openings I6a and I 6a have relatively large opposed axial components of velocity, compared to their total velocity, so as to cause these jets to intersect one another at a relatively large angle andat a position relatively close to the jet openings, so that a large number of particles propelled bygsuch jets will collide with high opposing axial components of velocities, providing an intense shattering effect. Although it will be seen that the jets issuing through openings I5a and |50.

` may also have opposed axial components of vevlocity, such components are relatively small as compared to their total velocity, so that the issuing jets intersect at a relatively small angle and at a considerable distance from the jet openings. Hence, particles propelled by these jets are likely to suiIer collisions with other particles in the grinding zone before reaching the position of intersection of the jet axes, and the jets issuing through openings I5a and lia will not function effectively to produce grinding by opposed jet action in the manner of the jets from openings 5 Ila and Ila', and are not intended primarily-for that purpose.

The material entering the paths of the opposed Jets issuing from openings Ita and Ilia' will be propelled at high velocity in the directions of such jets and will be subjected to grinding or size reducing action by impact and attrition resulting from the opposed axial components oi' velocity of colliding particles propelled by these two jets in the neighborhood of the position of intersection of these jets, as indicated at X in Fig. 3. Due to the centrifugal action resulting from the general whirling motion of the contents of the treatment chamber around the axis thereof, the larger particles of material are then caused to return to the peripheral portion of the grinding zone, where they are again acted upon by the jets issuing from the openings Ma, lia, Maf and lia', while the particles which have been sufficiently reduced in size are carried inwardly due to the entraining action of the irlwardly splralling gas.

The jets issuing from openings 14a, i5a, Ha and I5a" also contribute directly to the grinding action by imparting high velocities to material o intercepted thereby, and causing impact and attrition of such material with other particles of material circulating in the grinding zone, or against the walls of the treatment chamber. The material thus acted upon is also subjected to the vabove described centrifugal classifying action,

and the particles which are suiliciently reduced in size are entrained inwardly toward the gaseous fluid outlet of the treatment chamber.

p It is evident that the iiuid Jets from the openings Ila, I5a and Ita` in the upper portion of the grinding zone, and the jets from the openings` Ita' and I6a' in the lower portion of the lla', grinding zone, serve to superiinpose upon the general whirling movement of the material around theaxis of the treatment chamber positive circulatory motions in radial planes passing through the axis of said chamber as indicated by the arrows inFig. 1, and some of the material inthe grinding zone will therefore have a coinposite spiralling motion conforming to thatof a right handed screw in the upper portion, and a left handed screw in the lower portion of the grinding zone. It will also be seen that the curved peripheral wall portions of the treatment chamber, which extend around and at both axial ends of the grinding zone, have cross-sections in radial vertical planes composed of arcs of circles Varound the' centers, such as O and O', about which the superimposed circulatory motion in such radial planes is produced by the uid jets, so as to cooperate with the jets in maintaining the above described resultant-screw-like motion of the'material in the upper and lower portions of the grinding zone. l

The particles of material entrained inwardly from the grinding zone by the inwardly spiralling gas, together with any particles of material entering through the material inlet openings 26 which are already of a suiiiciently small size to be so entrained, are carried with the whirling gas into the centrifugal product collector 2l, where they are subjected to an intense centrifugal separating action, the material thus separated being discharged through the lower end of said collector, while the gaseous. fluid more or less freed of its burden of material is discharged through the central :duid outlet passage 22.

Fig. 4' is a vertical section of the outer portion vals of a modified form of grinding apparatus acn cording to this invention, taken in a radial vertical plane passing through its axis. 'I'his apparatus comprises a casing of circular cross-section enclosing a treatment chamber and including a top section 3l and a bottom section 3l', flanged exteriorly at their meeting faces and secured together by means of tie bolts 32. The peripheral portions 33 and 33 of the top and bottom casing sections are curved so as to provide annular grinding zone Z" at the outer portion of the treatment chamber enclosed at its periphery and at both axial ends by surfaces having an arcuate cross-section in a. radial vertical plane passing through the axis of the treatment chamber.

A plurality of jet openings 34, 35, 36 and 31 are' provided in the curved wall portions 33 and 33T at different angular positions about the center of curvature O" of the above mentioned arcuate surfaces. All the openings of this set are shown as positioned in a common radial vertical plane through the axis of the casing,l that is, in the plane of Fig. 4. It will be understood that any suitable number of such sets of openings may be provided at different angular positions around the axis of the casing in a manner comparable to that shown in Fig. 2 and it will also be understood that the successive openings 34, 35, etc., of each set may be angularly displaced from one another about the axis of the casing in a progressively advancing manner in the direction of whirling movement about said axis as more fully described hereinafter. Each of the openings 34, 35, 36 and 31 has a component of direction inclined in one direction with respect to a radial plane passing through the axis of the casingin order to maintain the whirling movement of the contents of the casing about the axis thereof, as described above in connection with Figs. 1 to 3,

`and each of these openings also has a component vthrough said axis.

Any'suitable means may be provided for supplying gaseous fluid under pressure to the above Vmentioned jet openings. The openings 34 and 35 are shown as provided-inthe curved wall portion 33' of the lower casing section 3|" and the openings 36 and 31 inthe curved Wall portion 33 of the upper casing section 3|. The respective casing'sections are shown as provided with annular fluid pressure manifolds 38 and 33' disposed exteriorly of the curved wall portions 33 and 33' and communicating with the openings 36, 31 and 34,

' 35, respectively, and said manifolds are provided with iiuid inlets 39 and 39' respectively.,v

The remainingportions of this apparatus may be substantially the same as above described, the annular material supply passage being shown at l4l and the material being delivered from said passage to the interior of the casing through openings-such as 42` comparable to the openings 26 above described.

Except for the omission of axially opposed jets such as those issuing from the openings 16a and |6a above, and theresultant'intensied grinding action due to such` lopposed jets, the operation of thisl form of apparatus is similar to that above described. Particles o! solid material which are brought into the annular grinding zone by the action of centrifugal force are subjected to the action of the high velocity fluid jets delivered through openings 34,v 35, V36 and 31. These jets will impart a spiralling motion similar to that of a right-handed screw, 'to the material accumulating along and adjacent the toruslike surface deiined by the curved wall portions 33 and 33' and particles of material entering the paths of these jets will be propelled at high velocity in the direction of the jets and will be subjected to pulverizing action by impact and attrition due to collisions thereof with other particles of material circulating in the grinding zone or against the walls of the chamber. Duetto the component of positive circulatory motion in radial planes passing through the axis of the chamber, which is superimposed upon the general whirling motion about the axis of the casing to provide the above mentioned screw like motion, the material is prevented from simply whirling aroundrv adjacent the peripheral walls in planes removed from the positions of the jets and is repeatedly picked up by the jets and positively directed into the zones of action of other jets either of the same set or of a succeeding set around the axis of the casing.

As in the form of apparatus first described, the gaseous fluid undergoes an inwardly spiralling action toward the centrally disposed fluid outlet, resulting in a continual classification of the material in the grinding zone` by the combined actions of centrifugal force and the inward entraining effect of the gas, so that particles which have been sufliciently reduced in size are carried inwardly and removed from the grinding zone while larger particles are returned toward the peripheral portion of the grindingv zone for fur- I ther action'by the fluid jets. y

Fig. 5 isa partial plan view of the apparatus similar to that shown in Fig.f4 and illustrates the above mentioned 'preferred arrangement of the Jet openings of each set in cases where the successive sets of jet openings are not disposed at sumciently small angular intervals around the treatment .chamber so rthat the 'jets delivered through one set of openings will vdirect material into the paths of jets of the next set. In this figure a set of four jet openings is indicated at 50',

34a, 35a, 36a and 31a, the upperv fluid pressure manifold 38 being partly broken away as indicated at 44 to better show the openings 36a and 31a in the upper curved wall portion 33 of the casing, and the upper casing section 3l being partly broken away asv indicated at 45 to better show the openings 34a and l35a in the curved wall portion 33 of the lower casing section 3l. This view illustrates the inclination of the axes of the respective jet openings with respect to radial planes passing through the axis of the casing as indicated by dotted lines representingv the projection traces of the respective jet axes on the plane of the figure, and the directions of these components of inclination of tliese openings as thus illustrated may be taken as illustrative of the correspondingcomponents of inclination oi.' jet openings 34 to 31 in Fig. 4. Similarly, it will be understood that the jet openings 34a to 31a also have components of inclination in one direction with respect to radii of curvature of the wall portions 33 and 33' in radial planes passing ythrough the axisof the casing comparable to the components of. inclinatiod represented by the .dotted projection traces or the openings u to n 2,191,095 '7 in F18 4. In this 038. hQWeVel'. the iet Opena median plane through the jet axis would be ings are shown as staggered or angulariy distangent to the periphery of the-chamber so that placed from one another about the axis of the approximately half of the gaseous duid would be casing so that the positions of the successive openings 34a, 35a, etc., conform substantially to the path of the above described screw-like motion of the material lalong the torus-like surface of the grinding zone. Thus the jet opening 35a, which succeeds the jet of the superimposed circulatory motion in radial planes through the axis of the casing, is angularly displaced from the opening a in the direction of whirling movement yabout the axis of the casing in such manner that material pro-A pelled by the fluid jet from opening 34a will be directed into the path of the fluid jet from the opening 35a as may be seen by comparing the dotted projection traces of the jets 34 and 34a in Figs. 4 and 5. Similarly thejet openings 38a and 31a are offset angularly about the axis of the casing with respect to the preceding jet openings 35a and 36a respectively. The ilrst jet opening of a succeeding set may be llocated, for

example, as indicated at' 34h, the position andV direction thereof; corresponding to opening 34a and being angularly oil-set from opening 31a in the direction of whirling movement around the axis of the casing.

Such an arrangement of' the iet openings will serve to provide an effective pulv`erizing action on the material due to direct collision or impact of particles propelled by'one jet with particles propelled by another jet and will also serve to bring a high proportion of the material in the grinding zone into the zones of action of the successive jets. It will be understood that a similar oi-set or staggered arrangement of the jet open.. ings of each set around the axis of the casing may also be applied to the jet openings of each set in the upper and lower portions of' the grind ing zone, in the form ofapparatus shown in Figs. 1 to 3.

' Inthe form of apparatus illustrated in Fig. 4 or Fig. 5, it will be understood that the sets of jet openings `disposed at different angularpositions around the axis of the treatment chamber may have oppositely directed components of inclination with `respect to radii of curvature of the walls in radial planes passing through said axis, so that some of the sets of jets serve to produce a right-handed screw-like spiralling motion and other sets of jets serve to produce a left-handed screw-like spiralling motion.

Also, it will be understood that in any of the forms of thel apparatus shown,A some of the jet openings may be of different size than other jet openings, and that separate fluid pressure manifolds or passages may be provided for supplying gaseous fluid at different pressures to diderent jet openings.

Itwill be seen thaiJ according to the present lnvention all of the fluid jets introduced into the grinding zone are given components of velocities normal to'the adjacent wall portions of the treatment chamber. In this manner the high velocity range of the issuing jets, bringing about the maxi `mum impact forces, is dissipated in regions removed from the walls ofthe chamber which minimizes frictional wear of thewalls.` Furthermore, it will be evident that any plane passing through the axis of a jet would have substantially an equal amount of gaseous fluid flowing on either side thereof. This excludes the possibility of using jets whose axes are truly tangent to the periphery of the treatment chamber, since with such a jet.

open ua in the direction' diverted to the outside oi' the chamber instead of into the interior thereof. Such a construction is' while the grinding eiiiciency of the jets is not ap` preciably reduced and is in increased. l

I claim: Y 1 l. Inra centrifugal fluid jet pulverizing apparatus for pulverizing solid materials by impact and attrition of particles upon one another, the commany cases materially bination of a casing of circular cross-section enclosing an annular grinding zone in the outer portion thereof, said casing having peripheral walls extending around and at both axialends of said grinding zone and curved in radial planes passing through theA axis of the casing to provide a surface of arcuate cross-section in such radial planes, said peripheral wallsbeing provided with jet openings forintroducing high vvelocity'fluid jets into said grinding zone in directions having components inclined forwardly in onel direction with respect tosuch radial planes in order to maintain whirling motion about said axis, said jet openingsincluding at least one set comprising a plurality of openings located at different angular positions about the center of curvature of said arcuate surface in such radial planes and the components of direction, in such radial planes, of all of the openings oi' saidV set being inclined in one direction with respect tothe radii of curvature of said arcuate surface at the positions of the respective openings and ,being inclined at dif-.-

ferent angles with respect to the axis of the casing, whereby the fluid jets issuing from the diiferently locatedV andv directed openings of said lset will cooperate to superimpose upon such whirling motion a positive circulatory motion in such radialA planes, and means for supplying gaseous fluid at high-pressure to said jetopenings.

2. In a centrifugal fluid jet pulverizing apparatus for pulverizing solid materials by impact and attrition of lparticles upon one another, 'the conibination of a casing of circular cross-section enclosing an annular grinding zone in the outer portion thereof, said casing having peripheral walls extending around and at both axial ends of said grinding zone and provided with jet openings for introducing high velocity jets into said grinding zone in directions having components inclined forwardly in one direction with respect to radial planes passing through the axis of said casing in order to maintainwhirling motion about said axis, said jet openings including a plurality of angularly spaced pairs of openings locatedy substantially opposite one another in a direction parallel to said axis and inwardly from the outer periphery of the grinding zone. the respective openings of each such pair having opposed components of direction parallel to said axis and being so` directed that the opposed fluid jets issuing therefrom'will intersect one another at positions inwardly removed from the outer periphery of the grinding zone, and said jet openings also comprising other openings which are located at greater radial distances from said axis than said oppositely located d openings and which are so positioned and directed that the fluid jets issuing therefrom will have components of velocity inclined with respect to the components of velocity of said opposed jets, in radial planes passing through said axis, and will superimpose upon the whirling motion about the axis of the casing, within the respective axial end portions of said grinding zone, opposite circulatory motions in such radial planes in such manner as to act upon material adjacent the periphery of the grinding zone and positively direct such material into the paths of said opposed jets, and means for supplying gaseous fluid under pressure to said jet openings.

3. In a centrifugal uid jet pulverizing apparatus for pulverizing solid materials by impact and attrition of particles upon one another, the combination of a casing of circular cross-section enclosing an annular grinding zone in the outer portion thereof, said casing having peripheral walls extending around and at both axial ends of'.

said grinding zone, the portions of said peripheral walls adjacent the respective axial ends of the grinding zone being curved in radial planes passing through the axis of the casing to provide two `surfaces having arcuate cross-sections in such radial planes and whose centers of curvature in of said casing in order to maintain whirling motion about said axis, said jet openings including a pluralityof angulaxly spaced pairs of open` ings located substantially opposite one another in f a direction parallel to said axis and inwardly from the outer periphery of the grinding zone, the respective openings of each such pair having op1 posed components ofy direction parallel to said axis and being so directed that the opposed fluid jets' issuing therefrom will intersect one another at positions inwardly removed from the outer periphery of the grinding zone, and said jet openings also comprising a plurality of other openings which are located at a plurality of diierent angular positions about said center of curvature of each of said arcuate surfaces and at greater radial distances from said axis than said oppositely located openings, and which are so posi tioned and directed that the iiuid jets issuing therefrom will have components of velocity in,l

" such manner as to act upon material adjacent the periphery of the grinding zone and positively direct such material into the paths of said opposed jets, and means for supplying gaseous fluid under so 

